cb125 oil leak, crankcase breather

[lozza59]

hi all
when i first got the bike it would wee all over the path outside the house, came from the same place as it does now, the crankcase breather pipe, also what comes out is oil mixed with a white substance, must be a lot of pressure in there right?
i did a top end rebuild, how would i know if i got the timing right? i mean if i got it a tooth off either way it would still run but with problems right?
another thing i did was i took off the rocker cover and started the bike, the left hand side of the cam with the clip gets great oil supply and the other side seems to just get a drizzle,
i took the rockers off to check the little metal dowel wasnt obstructing it and removed it all together, still the same,
my lack of knowledge is pushing me towards just finding another engine for it. would like the original sorted but that would cost me a fortune im sure. any help appreciated

[Teflon-Mike]

The white stuff in the oil is 'mayonase', an emulsion of oil and water.
You get it most often on engines that dont get warmed up properly and only do short runs, from the condensation in the crank case.
Oil should be changed at 1,250 miles, OR every six months, which ever is the sooner..... if bike doesn't do many miles, but gets left to sit, without time based oil changes, condesnation mayo builds up over time.
Also a sign of a head gasket failure.... but only on water cooled engines.
Oil from breather?
Well, have a pair of cases on my kitchen door as I type..... the breather vent is on the top of the gearbox enclosure, and it vents from another chamber forming a 'labertine trap'... basically a convolution of 'path' with a small sump, between the actual crank case and the vent. Sits above the level of gear oil, so that as pistons fall and rise any change in volume can be accomdated by air being sucked into the case, or dispelled, without blowing out any oil....
Older engines vent quite notoceably; often if you have worn or gummed piston rings, causes high crank case pressure from 'blow by' and you also get quite bad oil 'charring' from hot combustion gasses hitting exposed oil.
You have just done top end rebuild..... have you cracked a ring, putting pistons in?
BUT, may be a far simpler reason...
How are you checking the oil?
No idea about the cam journal oil feed...
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[lozza59]

thanks for your reply Mike
i run the bike again today up the road and when i got back i put it on stand on top of a large white bit of wood, and oil and mayo is coming out still, its also having trouble engaging the gears sometimes i put it into gear and it revs like its in neutral and sometimes even engages while im revving it, strange as once its going its ok.....
i got angry with it and gave the engine a hammering earlier, quite suprised with the result, i do wonder if my speedo is accurate but with standard gearing it does 40mph in 2nd gear and 60 in 3rd topped out at 72 ish in 4th .. does your cb125 do the same?
ive sourced another engine for 80 quid bloke said it is a good runner, i might have it until i get mine sorted. thanks again

[Teflon-Mike]

On stick geearing (15T front, 39T Rear Sprox, & standard tyre sized (3.00 front, 3.25 rear)
If you do the maths on quoted rduction ratio's,
At the 12K red line you would get:

33.60 mph from 1st gear
49.43 mph from 2nd gear
64.17 mph from 3rd gear
76.43 mph from 4th gear
85.89 mph from 5th gear

Speedo can over read by anything, but 5mph is typical. And the Tacho's arn't always so accurate, but, ball park isn't far off, though you'll struggle to max out in 4th, and 5th is pretty much an 'over drive' just to knock revs back.

Max power is at 10,500rpm, which givs a top sped of 75.15 in 5th... and it's not far off.

I was running the corporal on 14T front sprocket:

31.36 mph from 1st gear
46.14 mph from 2nd gear
59.89 mph from 3rd gear
71.34 mph from 4th gear
80.16 mph from 5th gear

Gives, 70.15mph at 10,500, in top..... which, is about what I have got out of it, clocked on GPS, but the speedo was off the scale past 80, and the tacho was burried well into the red!

The bike's forte, though is it's mid range. They struggle at the top end, and take a fair bit of winding up to eek that last few mph out of them. The shorter 14T sproket seems to help, mak th gearing a bit more useable.

Critical 50Kph for Mod 1, comes up at 11,500 in first, but you have to be in 2nd or 3rd when you come through the loop; with 15T, its just before 8K, 2nd, or 6K 3rd... With 14T it puts 50K right slap on th red line in 1st, so you really have to use 2nd, when it comes up at just over 8K, or 3rd whn it comes up at 6,5...
Th 'Pup' is also running CG tyre sizes... easier to get decent fitment, for the loss of 1/2" of rubber either end, you can get softr rubber, that's better supported, with less side wall. Gives slighly better handling; steering is lighter and more responsive, from smaller rolling diameter; but slightly lower gearing. Pushed 50Kmh, into the red beyond 12K in 1st, and just undr 8,5 in 2nd, and slap on 6.5 3rd... so we're swapping the 14T onto th Pup for Snowie to do tests on....

The biks dont really have the power to pull the claimd 75mph top speed, under anything but ideal circumstances anyway, and 5th is way over geared for what it can really pull.
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[lozza59]

wow unbelieveable!!!
on a 125 too!
amazing little bikes
at one time i thought of getting a cbr 125 motor to see if i could get that in there, still think about it sometimes.. but i would feel as though i might be wrecking the bike, the engine kind of makes it what it is.
i was just shocked when i looked down and saw 40 with it screaming in 2nd. i know none of my other 125cc bikes ever did that, might have pushed 35 in second from a kymco once.
thanks for the info

[Teflon-Mike]